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Post by kiwicanfly on Nov 26, 2017 8:58:00 GMT
It was Speed Weekend in Taranaki this weekend.
Day one was a simple 400m standing start sprint, not exactly a drag as reaction time was not measured. Recorded 13.5 seconds.
Day two was a hill climb, 2.5km of reasonably fast sealed road.
On run two I recorded 2:01 and was determined to go under 2:00.
Achieved it on run three, three seconds faster but I literally only just crossed the line!
The combined times were enough for second place in the C class.
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Post by buildityourself on Nov 26, 2017 19:57:49 GMT
wow, lucky it wasn't on the bend with the steep drop to the side. Do you have paddle shift gears?
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Post by kiwicanfly on Nov 26, 2017 21:07:33 GMT
The big sweeping right hander just prior to this is the one we were all concerned about, I knew that after that there were only the two "mild" left handers to go before the finish so kept it planted. I think it is the first time anyone has finished backwards before  I clipped and moved the timing gear but luckily still recorded a time  New Zealand roads don't take prisoners! |
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Post by kiwicanfly on Nov 26, 2017 21:10:49 GMT
I do have paddle shifters, it is the Hadron System developed by turbosteve |
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Post by Stiggy on Nov 28, 2017 22:03:23 GMT
any damage ?
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Post by kiwicanfly on Nov 28, 2017 23:19:08 GMT
Mainly cosmetic, the front grille is bent beyond repair but that had had some abuse previously and is an easy replacement. My main concern in the lower wishbone mounts, one of those looks a little bent, not big but noticeable. I am going to strip the front end down, clean off the paint and crack test them. Then plan to beef them up rather than put a brace on. I had checked them only the day before and was concerned I might be getting stress issues (old brace or no brace issue), however now is a definite plan before I take her out again. The car drove perfectly well back down the hill to the start with no running or handling issues but I opted out of a final run to be on the safe side and because I doubted I would improve my time, not because I couldn't go faster more that I would be unlikely to go faster after such an incident. Of course the main problem is that car is now no longer Red and Shiny Incidentally I had to remove soil from both the front and rear of the car, at the rear it was embedded in the exhaust mounts so it was a good spin! |
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Post by Stiggy on Nov 29, 2017 8:41:48 GMT
It would be useful to see pictures of the damage. I note you didn't have the brace bar fitted but in this case it would probably have served to cause both sides to bend as the energy would transfer to the side that was not hit. I noticed the left wheel was way out of track after the hit. I wonder if a solution for the future way involve a weak link, strong enough for the job but not if it is hit hard. This way if you hit something hard in future it will break away a wishbone without damaging the chassis or mounts or paint. Maybe a carefully placed and selected shear pin. Note when the F1 guys touch wheels that a bone can snap off and they quickly return to the pits on 3 wheels for a rapid turn around. link |
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Post by kiwicanfly on Nov 29, 2017 9:30:15 GMT
Just looked at the video again and take your point about left wheel however I think it must just be the way it's sitting as it looks OK currently sat on flat ground.
The damage to the mount I refered to was right side.
Going to strip the lot and check each part for damage.
Engineering a weak link is fraught with danger, getting it to only fail certain certain loads is above my pay grade.
Will post pics before I strip it.
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Post by Stiggy on Nov 29, 2017 10:17:39 GMT
It looked like both sides got a thump. Locaterfields use M10 bolts for suspension, you have M12's. So it may just be that machining a slot in the bolts may weaken them enough to shear under high impact but not in general use. An M10 is much less than 10 dia at the base of the thread cut so there is plenty to go at in determining a suitable slot depth in M12's. Thousands of 7's out there with shankless bolts (screws) so they are actually only attached by about 8 mm dia. Bolts should have shank, not thread at the point they go through the brackets. Torque settings will be lower of course once a slot is cut.  |
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Post by kiwicanfly on Nov 29, 2017 21:15:38 GMT
It looked like both sides got a thump. I was off the ground completely at one point and the left side came down first, so yeah it did get a thump both sides back and front in reality. Locaterfields use M10 bolts for suspension, you have M12's. So it may just be that machining a slot in the bolts may weaken them enough to shear under high impact but not in general use. Had to look up what a Locaterfield was! Are you saying that they use the 'modified' bolts in those builds or just they are built with smaller bolts, M10 v M12? An M10 is much less than 10 dia at the base of the thread cut so there is plenty to go at in determining a suitable slot depth in M12's. Root diameter of M10 is around 8mm. However what grade bolts are they using? If standard cap heads they will, most likely, be g12.7 whereas I am using SSA2-70 thus my bolts are already lower tensile, however clearly not enough to shear. Thousands of 7's out there with shankless bolts (screws) so they are actually only attached by about 8 mm dia. Bolts should have shank, not thread at the point they go through the brackets. Torque settings will be lower of course once a slot is cut. NZ requires a shank on all critical bolts unless too short to accommodate one, mine all have shanks. I've noticed a number of builds that use dome heads instead of cap or hex, these always come without shanks. Where did the picture you posted come from? I see the idea but to be honest I am not comfortable with the idea of simply cutting a groove in my bolts, I would be happier to use manufactured bolts of that type if the maths were there to support the practice. However it is quite interesting. |
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Post by Stiggy on Nov 29, 2017 22:54:50 GMT
they have been making 7's for 60 years, my guess is that every type of 10 mm bolt under the sun has been used, I am not aware of any failures of suspension bolts.
So the answer is either leave as is and try not to hit anything else or become a pioneer of shear bolts for kit car suspension by making something similar to the ones shown in my picture from a snow mobile.
Or repair the chassis each time an obstacle gets in the way.
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Post by Stiggy on Nov 29, 2017 23:02:34 GMT
a common bolt used on locost builds is an 8.8 10 mm 1.5 pitch and 7's are front engined. So it could be considered that 12.9's 12 mm cap heads in a rear engined Rocket are too tough, will not shear and ensure the chassis brackets are likely to fail under impact.
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Post by kiwicanfly on Dec 2, 2017 8:01:08 GMT
Pictures as promised. Front end damage mainly sustained by the grille, to be fair a lot of the paint damage came from the gravel the previous month at the Manfield track, time for a new grille methinks.  Damage to right side front mount, a little distorted and there is a small crack at the original bend.  Cracking of the weld at the back side of the mounting bracket.  The left side mount is also showing cracking at the weld, I don't know if that was increased by the impact as I had spotted it just prior to the event as was going to give a good checking anyway.  I also found that the radiator fan had broken free from its mounts and was just sitting against the radiator. Cant see any further damage, not that I want any! So I am going to strip the front end down completely, remove paint to bare metal at the front mounts and do a crack test then get a welder in to undertake the repairs. I will also beef up the mounts as well at the same time. I will also check every other weld for paint cracking and generally check for bends or distortions. As for Stuarts ideas of using modified bolts - I appreciate the thoughts and ideas behind it but I am not sure I want to be a guinee pig for that but I will look further into it later. And for Christmas I am getting a six point harness! |
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Post by kiwicanfly on Dec 3, 2017 9:04:33 GMT
Stripped the front end down today both of the lower front A arm rear mounts are also bent Now the lower A's are off the distortion to the front rhs is even more evident. Am wondering if the time reduction on that run was worth the damage..............nah course it was |
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Post by Stiggy on Dec 3, 2017 10:40:51 GMT
Very impressed with how the chassis stood up to the impact. Slight distortion and a weld starting to crack shows us that the thing is tough. You hit a fairly hard bank with the corner of the car, the delicate bit held it's own, excellent.
You just need to reduce bolt strength/dia to the same as 7's just in case you hit something else in future.
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